This invention relates generally to modifications to sportboards, and more particularly to surf boards, windsurfers, or snowboards with pivotable fin assemblies that allow the sportboards to be propelled forward by the user""s feet.
Many sports involve moving over water or snow while standing on one or two boards or blades. Surfing, snowboarding, and windsurfing are examples of sports that require the participant to stand on a single board that is supported by water or snow. In these sports, the board is moved forward by wave energy, gravity, or wind, respectively, while the participant steers by shifting his or her center of gravity or by moving a sail.
Propelling the board when the standard source of energy is absent can be problematic. Surfers normally lie on the surfboard and paddle with both arms to move opposite the flow of wave energy. This is a very traditional part of surfing but has some drawbacks. Paddling is slow and requires very strong shoulders and back. The prone position makes it hard for the surfer to see obstacles and requires the head to be held up in an uncomfortable position.
Snowboarders often release one boot from its binding and use that foot to propel the snowboard on level snow, much like a skateboard. In addition to the necessity of releasing and refixing the binding, the weight shift needed to push, then glide, is unstable and requires the attached leg to be turned at an unnatural 90xc2x0 angle, thus can cause falling. Pushing against soft powder snow with a boot is inefficient and can also lead to a fall when the boot sinks deeper than expected.
A snow skier can move rapidly forward on level ground or on a slight uphill incline by employing the skis independently in a technique called skating. Each ski in turn is pivoted at an angle from the direction of forward movement, rotated relative to the surface of the snow, and pushed against the snow in a direction substantially opposite to the desired direction of travel.
The present invention uses a similar technique to allow a single sport board to be propelled forward by means of two independently-pivotable fin assemblies. Although similar to skating, the technique is also closely allied to sculling or the motion of some fish. By altering the shape and size of the fins, this invention can be used on water for surfboards and windsurfers or on snow by snowboards or sleds.
The present invention provides a means for sport boards to be propelled by the user""s own energy when necessary. The propelling means is operable while in a standing position and actuated by the powerful muscles of the legs.
Also, the propulsion means of the present invention does not interfere with the functioning of the sportboard while employed for its primary use of harnessing wave, wind, or gravity power. Using this means for propelling the sport board is interesting, novel, and fun.
This invention is a user-propellable sportboard for moving over water or snow. Although typically accelerated by the force of wind, waves, or gravity, the sportboard can alternatively be propelled by the user""s muscle power when the preferred element is lacking or not moving in the desired direction.
In a preferred embodiment, the sportboard includes two pivotable fin assemblies, each of which is powered and controlled by one of the user""s feet. Each fin assembly comprises a foot platform, a fin, and a transmission shaft to transfer torque from the foot platform to the fin.
Typically, the sportboard of the present invention has two fin assemblies mounted on it. The foot platform may be above the deck of the board or may recessed into it. The user""s foot engages a platform by means of a binding, stirrup, or frictional surface.
The user""s foot is pivoted to pivot the platform. A transmission means, such as a shaft, connects the platform to the base of the fin, typically by passing through a hole bored through the body of the board. The shaft transmits the pivoting motion of the platform to the fin.
The fin pivots and exerts force on the water or snow under the board. By properly coordinated foot and body movements, the user produces a sculling effect that propels the sportboard forward. The fin assemblies can work in unison by pivoting the feet in tandem or can yield a stronger propulsion effect when operated independently. The optimal shape and size of the fins will vary according to condition of the snow or water and expertise of the user. If desired, gears are included in the transmission means to increase the power of the stroke.
Fin assemblies can be mounted such that they are semi-permanent, or easily demounted in the field. The user may change fin type to suit conditions, or may prefer to use the sport board without fins.
The sportboard is propelled by a person standing on the platforms, allowing use of the leg muscles for propulsion, good visibility, and a comfortable position of the neck. The fin assemblies can be operated with very little skill or practice, but are employed more efficiently and elegantly after some practice. This makes use of the propulsion means challenging and enjoyable both for a novice and for a more skilled user.